function Bola(){
	this.x = barra.x + barra.w/2;
	this.y = barra.y - barra.h;
	this.vx = 0;
	this.vy = 0;
	this.w = 20;
	this.h = 20;
	this.started = false;
}

Bola.prototype = {
	start: function(){
		if(this.started == false){
			this.started = true;
			this.vx = Math.random()*5;
			this.vy = 0;
			if(this.vx  < vConstante){
				this.vy = Math.sqrt((this.vx - vConstante) * -1)*-1;
			}else{
				this.vy = Math.sqrt(this.vx - vConstante);
			}			
		}	
	},
	move: function() {			
		this.x += this.vx;
		this.y += this.vy;
	},
}